I'll say what everyone is saying – the controls are unresponsive.
The main problem, which you might want to consider fixing, is not being able to change your mind once you start moving. You press A – that's it, now you have to wait until you fully slide to the left before you can move again. What about interrupting the current movement if you press the opposite direction? And perhaps making it slightly faster?
You basically have three fixed "1 2 3" points on the screen where the player can be, so hopefully, it wouldn't be too hard to swap the current movement target e.g. from 1 to 2 mid-way.
As for loading times, I suggest you try the free add-on "Scene Streamer". It should be perfect for your game since you essentially have a single long corridor which you can load in parts.
https://assetstore.unity.com/packages/tools/utilities/scene-streamer-38168
Then I think the game doesn't exactly invoke "Fear". If it wasn't for the music, then there would be nothing scary at all. I also like the colour scheme shown in the thumbnail much more.
If you wanted to add another gameplay element, you could consider jumping (e.g. over a hole or a small obstacle).
Some bugs/other things I found:
– Go from left to right and right to left very quickly. Quite often "D" will get stuck and you'll be unable to move right for a while.
– Die on the upwards slope. Now if you restart the game, the slope modifier will still be applied and the player will fly up.
– In the console, the game complains about a missing MonoBehaviour on game object 'GM'. Are you restarting the game correctly?
– Graphical bugs – the ground seems to flicker. There's either a problem with the material/texture or it's two objects overlapping each other at the same height (so the engine doesn't know which one to render)
– It doesn't look (or sound) like the sphere is rolling but perhaps it is
– 'Level Failed' message looks exactly like a button but it isn't interactable. And perhaps wait a short while before showing it – sometimes you don't even realise what hit you.
It works, there's some gameplay, but I wouldn't exactly consider it finished or enjoyable.